The computer and electronics industry demand of increasing its whole speed performance as well as its cost down for fabricating integrated circuits. As far as a computer is concern, it is without doubting that the DRAM integrated circuits plays a crucial role because it is used by a large number and it plays a vital factor for determining the I/O speed in a computer. Hence, pursuing the miniaturization of the DRAM device as well as high-speed performance are almost the ultimate goals.
For pursuing high-speed requirement, the DRAM cell's storage capacity is an important factor to be considered. The capacitor is formed with a storage node, a cell plate, and an intervening dielectric layer. Thus the storage capacity could be increased by making the capacitor dielectric layer thinner, by using an insulator with a large r dielectric constant, or by increasing the area of the capacitor. The first two options are not viable, since capacitor dielectric layers thinner than those now being used in DRAM cells will suffer leakage current due to Fowler-Nordheim tunneling. Moreover, it will also deteriorate the oxidation resist. However, the suffering from a higher leakage current for using a larger dielectric constant layer is being reported in some research. Thus, most approach is by means of increasing the surface area of the bottom cell plate. For instance, the crown-shaped capacitor or fin shaped capacitor or the cylindrical shaped capacitor so as to increase the capacitance. The integrity of about 256M or 1 Giga bytes DRAM capacitor in a chip, the present design rule is, however, can not be satisfied when utilizes merely by increasing the surface area of the bottom cell plate. The lithographic and etching issues are suffered due to the high aspect ratio of the contact hole.
Thus, improving the effective dielectric constant of the capacitor dielectric layer without the leakage current issue to obtain the large capacitance may be the best approach to alleviate the burden of the lithographic and etching technique
The present invention provides such a method.